In general, soybean which is one of the pulse crops contains isoflavone compounds including daidzin, daidzein, genistin and genistein.
The isoflavone compounds are represented by the following formula and Denotative Table.
______________________________________ ##STR1## Denotative Table R1 R2 ______________________________________ daidzin H glucose daidzein H H genistin OH glucose genistein OH H ______________________________________
Of these isoflavone compounds, daidzein is an aglycone of daidzin having its glucose as a glycosidic saccharide hydrolytically separated therefrom, and genistein is an aglycone of genistin having its glucose as a glycosidic saccharide hydrolytically separated therefrom. With respect to the isoflavone compounds, contents thereof and percentages between daidzin and daidzein and between genistin and genistein in a defatted soybean are as shown in the following Table 1.
TABLE 1 ______________________________________ daidzin daidzein genistin genistein ______________________________________ defatted soybean 100 3.2 180 4.2 (96.9%) (3.1%) (97.7%) (2.3%) ______________________________________ (unit: mg/100g)
It is understood from Table 1 that, in soybean, daidzin and genistin are contained in larger amounts while daidzein and genistein which are aglycones thereof are contained in smaller amounts.
On the other hand, it has been reported that a glycosidic saccharide is hydrolyzed from an isoflavone compound contained in soybean to form an aglycone in the course of soy sauce or miso (fermented soybean paste) preparation see Sho-Ken (Soy-research) by Kiyoshi Kihara, vol.16, No.5, page 190 (1990)!.
According to this report, however, although hydrolysis of a glycosidic saccharide proceeds to some extent by cooking of a defatted soybean or in a koji preparation step, most of the saccharide has already hydrolytically been separated in soy sauce sediment or soybean miso. Accordingly, it is difficult to employ these for a process for preparing a product from a pulse crop as a starting material.
Further, many reports have been made on pharmacological activities of aglycones derived from hydrolysis of glycosidic saccharides from isoflavone compounds.
For example, genistein has been ascertained to be a tyrosine kinase inhibitor (TK inhibitor). Since tyrosine kinase is essentially responsible for cancer-induction by an onocogene, carcinostatic activities of genistein as a TK inhibitor are confirmed and the effect thereof has drawn attention Akiyama et al.: Biochemistry, vol.59, No.9, page 1016 (1987)!.
Further, estrogenic activities of an isoflavone compound have also attracted attention and have been confirmed to have osteoprosis therapeutic effect and immunosuppressive effect. In particular, genistein which is an aglycone of an isoflavone compound has notable estrogenic activities, and this activities enable osteopenia (bone resorption) to be suppressed.
Accordingly, many proposals concerning isoflavone compounds contained in soybean have been made in Japanese Unexamined Patent Publication No.126,186/1987, Japanese Unexamined Patent Publication No.258,669/1989, Japanese Unexamined Patent Publication No.170,756/1993, and so on.